1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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24
25 #ifndef SHARE_VM_MEMORY_CARDTABLEMODREFBS_HPP
26 #define SHARE_VM_MEMORY_CARDTABLEMODREFBS_HPP
27
28 #include "memory/modRefBarrierSet.hpp"
29 #include "oops/oop.hpp"
30
31 // This kind of "BarrierSet" allows a "CollectedHeap" to detect and
32 // enumerate ref fields that have been modified (since the last
33 // enumeration.)
34
35 // As it currently stands, this barrier is *imprecise*: when a ref field in
36 // an object "o" is modified, the card table entry for the card containing
37 // the head of "o" is dirtied, not necessarily the card containing the
38 // modified field itself. For object arrays, however, the barrier *is*
39 // precise; only the card containing the modified element is dirtied.
40 // Closures used to scan dirty cards should take these
41 // considerations into account.
42
43 class Generation;
44 class OopsInGenClosure;
45 class DirtyCardToOopClosure;
46 class ClearNoncleanCardWrapper;
47 class CardTableRS;
48
49 class CardTableModRefBS: public ModRefBarrierSet {
50 // Some classes get to look at some private stuff.
51 friend class BytecodeInterpreter;
52 friend class VMStructs;
53 friend class CardTableRS;
54 friend class CheckForUnmarkedOops; // Needs access to raw card bytes.
55 friend class SharkBuilder;
56 #ifndef PRODUCT
57 // For debugging.
58 friend class GuaranteeNotModClosure;
59 #endif
60 protected:
61
62 enum CardValues {
63 clean_card = -1,
64 // The mask contains zeros in places for all other values.
65 clean_card_mask = clean_card - 31,
66
67 dirty_card = 0,
68 precleaned_card = 1,
69 claimed_card = 2,
70 deferred_card = 4,
71 last_card = 8,
72 CT_MR_BS_last_reserved = 16
73 };
74
75 // a word's worth (row) of clean card values
76 static const intptr_t clean_card_row = (intptr_t)(-1);
77
78 // dirty and precleaned are equivalent wrt younger_refs_iter.
79 static bool card_is_dirty_wrt_gen_iter(jbyte cv) {
80 return cv == dirty_card || cv == precleaned_card;
81 }
82
83 // Returns "true" iff the value "cv" will cause the card containing it
84 // to be scanned in the current traversal. May be overridden by
85 // subtypes.
86 virtual bool card_will_be_scanned(jbyte cv) {
87 return CardTableModRefBS::card_is_dirty_wrt_gen_iter(cv);
88 }
89
90 // Returns "true" iff the value "cv" may have represented a dirty card at
91 // some point.
92 virtual bool card_may_have_been_dirty(jbyte cv) {
93 return card_is_dirty_wrt_gen_iter(cv);
94 }
95
96 // The declaration order of these const fields is important; see the
97 // constructor before changing.
98 const MemRegion _whole_heap; // the region covered by the card table
99 size_t _guard_index; // index of very last element in the card
100 // table; it is set to a guard value
101 // (last_card) and should never be modified
102 size_t _last_valid_index; // index of the last valid element
103 const size_t _page_size; // page size used when mapping _byte_map
104 size_t _byte_map_size; // in bytes
105 jbyte* _byte_map; // the card marking array
106
107 int _cur_covered_regions;
108 // The covered regions should be in address order.
109 MemRegion* _covered;
110 // The committed regions correspond one-to-one to the covered regions.
111 // They represent the card-table memory that has been committed to service
112 // the corresponding covered region. It may be that committed region for
113 // one covered region corresponds to a larger region because of page-size
114 // roundings. Thus, a committed region for one covered region may
115 // actually extend onto the card-table space for the next covered region.
116 MemRegion* _committed;
117
118 // The last card is a guard card, and we commit the page for it so
119 // we can use the card for verification purposes. We make sure we never
120 // uncommit the MemRegion for that page.
121 MemRegion _guard_region;
122
123 protected:
124 // Initialization utilities; covered_words is the size of the covered region
125 // in, um, words.
126 inline size_t cards_required(size_t covered_words) {
127 // Add one for a guard card, used to detect errors.
128 const size_t words = align_size_up(covered_words, card_size_in_words);
129 return words / card_size_in_words + 1;
130 }
131
132 inline size_t compute_byte_map_size();
133
134 // Finds and return the index of the region, if any, to which the given
135 // region would be contiguous. If none exists, assign a new region and
136 // returns its index. Requires that no more than the maximum number of
137 // covered regions defined in the constructor are ever in use.
138 int find_covering_region_by_base(HeapWord* base);
139
140 // Same as above, but finds the region containing the given address
141 // instead of starting at a given base address.
142 int find_covering_region_containing(HeapWord* addr);
143
144 // Resize one of the regions covered by the remembered set.
145 virtual void resize_covered_region(MemRegion new_region);
146
147 // Returns the leftmost end of a committed region corresponding to a
148 // covered region before covered region "ind", or else "NULL" if "ind" is
149 // the first covered region.
150 HeapWord* largest_prev_committed_end(int ind) const;
151
152 // Returns the part of the region mr that doesn't intersect with
153 // any committed region other than self. Used to prevent uncommitting
154 // regions that are also committed by other regions. Also protects
155 // against uncommitting the guard region.
156 MemRegion committed_unique_to_self(int self, MemRegion mr) const;
157
158 // Mapping from address to card marking array entry
159 jbyte* byte_for(const void* p) const {
160 assert(_whole_heap.contains(p),
161 err_msg("Attempt to access p = "PTR_FORMAT" out of bounds of "
162 " card marking array's _whole_heap = ["PTR_FORMAT","PTR_FORMAT")",
163 p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end())));
164 jbyte* result = &byte_map_base[uintptr_t(p) >> card_shift];
165 assert(result >= _byte_map && result < _byte_map + _byte_map_size,
166 "out of bounds accessor for card marking array");
167 return result;
168 }
169
170 // The card table byte one after the card marking array
171 // entry for argument address. Typically used for higher bounds
172 // for loops iterating through the card table.
173 jbyte* byte_after(const void* p) const {
174 return byte_for(p) + 1;
175 }
176
177 // Iterate over the portion of the card-table which covers the given
178 // region mr in the given space and apply cl to any dirty sub-regions
179 // of mr. Clears the dirty cards as they are processed.
180 void non_clean_card_iterate_possibly_parallel(Space* sp, MemRegion mr,
181 OopsInGenClosure* cl, CardTableRS* ct,
182 uint n_threads);
183
184 private:
185 // Work method used to implement non_clean_card_iterate_possibly_parallel()
186 // above in the parallel case.
187 void non_clean_card_iterate_parallel_work(Space* sp, MemRegion mr,
188 OopsInGenClosure* cl, CardTableRS* ct,
189 uint n_threads);
190
191 protected:
192 // Dirty the bytes corresponding to "mr" (not all of which must be
193 // covered.)
194 void dirty_MemRegion(MemRegion mr);
195
196 // Clear (to clean_card) the bytes entirely contained within "mr" (not
197 // all of which must be covered.)
198 void clear_MemRegion(MemRegion mr);
199
200 // *** Support for parallel card scanning.
201
202 // This is an array, one element per covered region of the card table.
203 // Each entry is itself an array, with one element per chunk in the
204 // covered region. Each entry of these arrays is the lowest non-clean
205 // card of the corresponding chunk containing part of an object from the
206 // previous chunk, or else NULL.
207 typedef jbyte* CardPtr;
208 typedef CardPtr* CardArr;
209 CardArr* _lowest_non_clean;
210 size_t* _lowest_non_clean_chunk_size;
211 uintptr_t* _lowest_non_clean_base_chunk_index;
212 int* _last_LNC_resizing_collection;
213
214 // Initializes "lowest_non_clean" to point to the array for the region
215 // covering "sp", and "lowest_non_clean_base_chunk_index" to the chunk
216 // index of the corresponding to the first element of that array.
217 // Ensures that these arrays are of sufficient size, allocating if necessary.
218 // May be called by several threads concurrently.
219 void get_LNC_array_for_space(Space* sp,
220 jbyte**& lowest_non_clean,
221 uintptr_t& lowest_non_clean_base_chunk_index,
222 size_t& lowest_non_clean_chunk_size);
223
224 // Returns the number of chunks necessary to cover "mr".
225 size_t chunks_to_cover(MemRegion mr) {
226 return (size_t)(addr_to_chunk_index(mr.last()) -
227 addr_to_chunk_index(mr.start()) + 1);
228 }
229
230 // Returns the index of the chunk in a stride which
231 // covers the given address.
232 uintptr_t addr_to_chunk_index(const void* addr) {
233 uintptr_t card = (uintptr_t) byte_for(addr);
234 return card / ParGCCardsPerStrideChunk;
235 }
236
237 // Apply cl, which must either itself apply dcto_cl or be dcto_cl,
238 // to the cards in the stride (of n_strides) within the given space.
239 void process_stride(Space* sp,
240 MemRegion used,
241 jint stride, int n_strides,
242 bool parallel,
243 OopsInGenClosure* cl,
244 CardTableRS* ct,
245 jbyte** lowest_non_clean,
246 uintptr_t lowest_non_clean_base_chunk_index,
247 size_t lowest_non_clean_chunk_size);
248
249 // Makes sure that chunk boundaries are handled appropriately, by
250 // adjusting the min_done of dcto_cl, and by using a special card-table
251 // value to indicate how min_done should be set.
252 void process_chunk_boundaries(Space* sp,
253 DirtyCardToOopClosure* dcto_cl,
254 MemRegion chunk_mr,
255 MemRegion used,
256 jbyte** lowest_non_clean,
257 uintptr_t lowest_non_clean_base_chunk_index,
258 size_t lowest_non_clean_chunk_size);
259
260 public:
261 // Constants
262 enum SomePublicConstants {
263 card_shift = 9,
264 card_size = 1 << card_shift,
265 card_size_in_words = card_size / sizeof(HeapWord)
266 };
267
268 static int clean_card_val() { return clean_card; }
269 static int clean_card_mask_val() { return clean_card_mask; }
270 static int dirty_card_val() { return dirty_card; }
271 static int claimed_card_val() { return claimed_card; }
272 static int precleaned_card_val() { return precleaned_card; }
273 static int deferred_card_val() { return deferred_card; }
274
275 virtual void initialize();
276
277 // *** Barrier set functions.
278
279 bool has_write_ref_pre_barrier() { return false; }
280
281 protected:
282
283 CardTableModRefBS(MemRegion whole_heap, const BarrierSet::FakeRtti& fake_rtti);
284 ~CardTableModRefBS();
285
286 // Record a reference update. Note that these versions are precise!
287 // The scanning code has to handle the fact that the write barrier may be
288 // either precise or imprecise. We make non-virtual inline variants of
289 // these functions here for performance.
290
291 void write_ref_field_work(oop obj, size_t offset, oop newVal);
292 virtual void write_ref_field_work(void* field, oop newVal, bool release = false);
293 public:
294
295 bool has_write_ref_array_opt() { return true; }
296 bool has_write_region_opt() { return true; }
297
298 inline void inline_write_region(MemRegion mr) {
299 dirty_MemRegion(mr);
300 }
301 protected:
302 void write_region_work(MemRegion mr) {
303 inline_write_region(mr);
304 }
305 public:
306
307 inline void inline_write_ref_array(MemRegion mr) {
308 dirty_MemRegion(mr);
309 }
310 protected:
311 void write_ref_array_work(MemRegion mr) {
312 inline_write_ref_array(mr);
313 }
314 public:
315
316 bool is_aligned(HeapWord* addr) {
317 return is_card_aligned(addr);
318 }
319
320 // *** Card-table-barrier-specific things.
321
322 template <class T> inline void inline_write_ref_field_pre(T* field, oop newVal) {}
323
324 template <class T> inline void inline_write_ref_field(T* field, oop newVal, bool release);
325
326 // These are used by G1, when it uses the card table as a temporary data
327 // structure for card claiming.
328 bool is_card_dirty(size_t card_index) {
329 return _byte_map[card_index] == dirty_card_val();
330 }
331
332 void mark_card_dirty(size_t card_index) {
333 _byte_map[card_index] = dirty_card_val();
334 }
335
336 bool is_card_clean(size_t card_index) {
337 return _byte_map[card_index] == clean_card_val();
338 }
339
340 // Card marking array base (adjusted for heap low boundary)
341 // This would be the 0th element of _byte_map, if the heap started at 0x0.
342 // But since the heap starts at some higher address, this points to somewhere
343 // before the beginning of the actual _byte_map.
344 jbyte* byte_map_base;
345
346 // Return true if "p" is at the start of a card.
347 bool is_card_aligned(HeapWord* p) {
348 jbyte* pcard = byte_for(p);
349 return (addr_for(pcard) == p);
350 }
351
352 HeapWord* align_to_card_boundary(HeapWord* p) {
353 jbyte* pcard = byte_for(p + card_size_in_words - 1);
354 return addr_for(pcard);
355 }
356
357 // The kinds of precision a CardTableModRefBS may offer.
358 enum PrecisionStyle {
359 Precise,
360 ObjHeadPreciseArray
361 };
362
363 // Tells what style of precision this card table offers.
364 PrecisionStyle precision() {
365 return ObjHeadPreciseArray; // Only one supported for now.
366 }
367
368 // ModRefBS functions.
369 virtual void invalidate(MemRegion mr, bool whole_heap = false);
370 void clear(MemRegion mr);
371 void dirty(MemRegion mr);
372
373 // *** Card-table-RemSet-specific things.
374
375 static uintx ct_max_alignment_constraint();
376
377 // Apply closure "cl" to the dirty cards containing some part of
378 // MemRegion "mr".
379 void dirty_card_iterate(MemRegion mr, MemRegionClosure* cl);
380
381 // Return the MemRegion corresponding to the first maximal run
382 // of dirty cards lying completely within MemRegion mr.
383 // If reset is "true", then sets those card table entries to the given
384 // value.
385 MemRegion dirty_card_range_after_reset(MemRegion mr, bool reset,
386 int reset_val);
387
388 // Provide read-only access to the card table array.
389 const jbyte* byte_for_const(const void* p) const {
390 return byte_for(p);
391 }
392 const jbyte* byte_after_const(const void* p) const {
393 return byte_after(p);
394 }
395
396 // Mapping from card marking array entry to address of first word
397 HeapWord* addr_for(const jbyte* p) const {
398 assert(p >= _byte_map && p < _byte_map + _byte_map_size,
399 "out of bounds access to card marking array");
400 size_t delta = pointer_delta(p, byte_map_base, sizeof(jbyte));
401 HeapWord* result = (HeapWord*) (delta << card_shift);
402 assert(_whole_heap.contains(result),
403 err_msg("Returning result = "PTR_FORMAT" out of bounds of "
404 " card marking array's _whole_heap = ["PTR_FORMAT","PTR_FORMAT")",
405 p2i(result), p2i(_whole_heap.start()), p2i(_whole_heap.end())));
406 return result;
407 }
408
409 // Mapping from address to card marking array index.
410 size_t index_for(void* p) {
411 assert(_whole_heap.contains(p),
412 err_msg("Attempt to access p = "PTR_FORMAT" out of bounds of "
413 " card marking array's _whole_heap = ["PTR_FORMAT","PTR_FORMAT")",
414 p2i(p), p2i(_whole_heap.start()), p2i(_whole_heap.end())));
415 return byte_for(p) - _byte_map;
416 }
417
418 const jbyte* byte_for_index(const size_t card_index) const {
419 return _byte_map + card_index;
420 }
421
422 // Print a description of the memory for the barrier set
423 virtual void print_on(outputStream* st) const;
424
425 void verify();
426 void verify_guard();
427
428 // val_equals -> it will check that all cards covered by mr equal val
429 // !val_equals -> it will check that all cards covered by mr do not equal val
430 void verify_region(MemRegion mr, jbyte val, bool val_equals) PRODUCT_RETURN;
431 void verify_not_dirty_region(MemRegion mr) PRODUCT_RETURN;
432 void verify_dirty_region(MemRegion mr) PRODUCT_RETURN;
433 };
434
435 template<>
436 struct BarrierSet::GetName<CardTableModRefBS> {
437 static const BarrierSet::Name value = BarrierSet::CardTableModRef;
438 };
439
440 class CardTableRS;
441
442 // A specialization for the CardTableRS gen rem set.
443 class CardTableModRefBSForCTRS: public CardTableModRefBS {
444 CardTableRS* _rs;
445 protected:
446 bool card_will_be_scanned(jbyte cv);
447 bool card_may_have_been_dirty(jbyte cv);
448 public:
449 CardTableModRefBSForCTRS(MemRegion whole_heap) :
450 CardTableModRefBS(
451 whole_heap,
452 // Concrete tag should be BarrierSet::CardTableForRS.
453 // That will presently break things in a bunch of places though.
454 // The concrete tag is used as a dispatch key in many places, and
455 // CardTableForRS does not correctly dispatch in some of those
456 // uses. This will be addressed as part of a reorganization of the
457 // BarrierSet hierarchy.
458 BarrierSet::FakeRtti(BarrierSet::CardTableModRef, 0).add_tag(BarrierSet::CardTableForRS))
459 {}
460
461 void set_CTRS(CardTableRS* rs) { _rs = rs; }
462 };
463
464 template<>
465 struct BarrierSet::GetName<CardTableModRefBSForCTRS> {
466 static const BarrierSet::Name value = BarrierSet::CardTableForRS;
467 };
468
469
470 #endif // SHARE_VM_MEMORY_CARDTABLEMODREFBS_HPP